Device and method for the treatment of breathing disorders and cardiac disorders

ABSTRACT

The present invention is related to an implantable medical device for treating breathing disorders and cardiac disorders by delivering stimulation energy to the phrenic nerve, hypoglossal nerves and cardiac muscle tissues.

CROSS REFERENCE TO RELATED CASES

The present case claims the benefit of U.S. Provisional Application60/881,695 filed Jan. 22, 2007 entitled Transvenous Stimulation ofHypoglossal Nerve to Treat Central and Obstructive Sleep Apnea. Thedisclosure of the provisional application is incorporated by reference.

FIELD OF THE INVENTION

An implantable medical device and a method carried out with animplantable medical device for the treatment of sleep apnea and for thetreatment of sleep apnea in patients with cardiac disorders.

BACKGROUND OF THE INVENTION

Sleep apnea (SA) is a disease state in which the patient exhibitsperiodic breathing. Sleep apnea is typically characterized as either“obstructive” (OSA) or “central” (CSA). Many patients exhibit thedisorder in both of its forms, OSA and CSA. OSA is traditionally treatedby attempting to maintain patency of the upper airway. CSA istraditionally treated by stimulation of the diaphragm. Sleep apneasoccur with high frequency in patients with cardiac rhythm disorders thatmight be treated with bradycardia treatment or biventricular pacemakers.

SUMMARY

The present invention includes a method, device, and system fortreatment of SA breathing. The system includes one or more transvenousleads coupled to an implanted medical device, where one lead system ispositioned to stimulate a muscle group. An additional lead system ispositioned to stimulate at least one nerve. In an alternative embodimentof the device, the two lead systems both stimulate nerves. In thisalternative embodiment, one set of nerves leads to muscle contractionand the other set of nerves do not lead to muscle contraction but theylocally alter the “tone” of the nervous system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the system in schematic form;

FIG. 2 depicts a process carried out in the implanted device;

FIG. 3 depicts a process carried out in the implanted device;

DETAILED DESCRIPTION OF THE INVENTION

The nervous system (NS) is exceedingly complex. Two main components ofthe NS are the sympathetic NS and the parasympathetic NS. It is widelyheld that these two systems counteract each other and a homeostaticbalance is achieved between them. It is recognized that the relativeactivation of the two systems results in a “tone” that that variesbetween waking and sleeping states.

Without elucidating a complete mechanism of action, the inventorscompleted a course of experimentation that suggests to them thattransvenous stimulation near the base of the tongue, near the locationof the hypoglossal nerves, increases airflow during apnea with outactually provoking activation of muscle tissue near the stimulationsite. Applicants believe that this sub-threshold stimulation alters“tone”. It should be understood that the measurement of tone is fraughtwith technical difficulties; However, the inventors believe that theperiodic and episodic application of electrical currents at voltages andcurrents far below the levels required for evoked muscle contraction oftissue near the tongue are responsible for an increase in the diameterof the airway passages and increase ventilation in patients. Theinventors believe that episodic background simulation may increase theotherwise prevailing level of tone and that this level of stimulation iscompatible with restful sleep and will not arouse a sleeping patient. Ineach embodiment of the inventors' system low-level stimulation istravenously delivered to nerves and muscles near the hypoglossal tissuesof a patient.

FIG. 1 depicts an implanted medical device 10 (IMD) of the typenecessary to carry out the invention. The IMD 10 is coupled to a firsttransvenous lead system 12 located in the area of the tongue near thehypoglossal nerves represented schematically at reference numeral 17 andplacing stimulation electrodes typified by electrode 23 in a vein orartery 13 near the hypoglossal nerves 17. A second lead system 14couples the IMD 10 transvenously to the phrenic nerve and diaphragmrepresented schematically at reference numeral 19. Once againstimulation electrodes are placed near the phrenic nerve as indicatedschematically at reference numeral 25. A third lead system 16 places apacing lead 20 in the right ventricle RV and a pacing lead 18 positionedto stimulate the left ventricle LV of the heart 21.

The IMD 10 contains conventional circuitry to detect the patients R-waveand impedance plythesmographic detectors to find the mid breath point inthe respiration cycle. The IMD 10 also contains an activity sensor tomeasure the activity level of the patient. This activity sensor may beused to detect periods of sleep. These sense amplifiers, stimulationpulse generators, activity monitors, and impedance monitors arestructures that are not described in detail as they are well known tothose skilled in this art.

Pacing Embodiment

The transvascular subtheshold low level stimulation of the hypoglossaltissues near the upper airways may be combined with conventionalbradycardia pacing therapies. Applicants describe a device that combineslow-level transvascular stimulation with a conventional pacing regime ormodality. Although the invention is applicable to both biventricularlead placements as well as cardiac defibrillator lead placements, theinvention is described in the context of a biventricular demand modepacemaker. It must be understood that other bradycardia and tachycardiatreatment modalities are contemplated and are within the scope of theclaims. The choice of the depicted modality is selected for simplicityand because it is indicated for patients likely to also suffer fromsleep apnea.

During periods of pacing support of the patient's rhythm the IMD 10 willalso delivers stimulation energy to the hypoglossal tissues via thetransvenous lead 12. The stimulation energy delivered may be continuousor intermittent at an appropriate relatively low frequency duty cycle.

At times when the patient's detected activity is low, the IMD maydeliver background stimulation from an appropriate pulse generatorwithin the IMD 10 through the lead system 12 at a level insufficient toarouse the patient from sleep.

FIG. 2 is a flowchart depicting representative implementation of theintegration of very low energy transvascular hypoglossal stimulationwith brady pacing. The process starts with block 100. In decision block120 the presence or absence of an R-wave is determined with a senseamplifier within the IMD 10. If an R-wave is detected (yes in process120), the process 120 resets the pacing escape interval timer andreturns to the start of R-wave detection process 120. If an R-wave doesnot occur within an escape interval (no in process 120), the processmoves to process 122 where patient activity is monitored. If the patientis inactive (no in process 122), perhaps asleep, and in need ofventricular stimulation, then the processes 124 activates the low levelhypoglossal tissues via lead system 12 while process 126 activates thebiventricular pulse generators to delivery stimulation on leads 18 and20. In this fashion the patient receives the low level hypoglossalstimulation in phase with pacing therapy. Other variations instimulation patterns are possible as well.

Respiration Embodiment

The IMD 10 is equipped to detect respiration and deliver stimulation tothe phrenic nerve via lead system 14 at times and stimulation magnitudesto “hold” the breath of a patient. This breath holding attribute tendsto decrease breathing rate and has been proposed by the inventors as atreatment for central sleep apnea.

In this embodiment low-level electrical stimulation of the tissues nearthe hypoglossal nerve is invoked and delivered at the time that phrenicnerve receives stimulation. FIG. 3 depicts a representativeimplementation of a software process carried out within the IMD 10 totreat a patient. In the start process 101 the IMD 10 turns on therespiration sensor system, and in process 130 the IMD finds themid-breath point. If appropriate (yes in process 130), the IMD entersprocess 132 where pulse generators within the IMD deliver phrenic nervestimulation via lead system 14 in synchrony with the mid breathrespiration point. The device moves to process 134 where low-levelhypoglossal stimulation is delivered via lead system 12. In this fashionlow-level electrical energy is delivered to the upper airway to improvepatency during a breath. In this way the invention overcomes limitationsof prior art that require:

-   -   1. surgical placement of nerve stimulation electrodes on the        nerve    -   2. synchronized stimulation that requires contraction of        selected airway muscles prior and during natural inspiration        phase of the breath    -   3. discomfort to the patient caused by stimulation of small        muscles in the head and neck

What is claimed is:
 1. An implanted medical device for treating apatient comprising: a stimulator providing electrical stimulation to afirst lead system and a second lead system; said first lead systemtransvenously placing stimulation electrode near the patient'shypoglossal tissues; said second lead system transvenously placingstimulation electrode near the patient's phrenic nerve.
 2. An implantedmedical device for treating a patient comprising: a stimulator providingstimulation to a first lead system and a second lead system; said firstlead system transvenously placing stimulation electrode near thepatient's hypoglossal nerve; said second lead system transvenouslyplacing stimulation electrode in a chamber of patient's heart.
 3. Thedevice of claim 1 wherein said stimulator supplies sub thresholdstimulation periodically to said first lead system to alter hypoglossaltone to a value near the value of tone during the awake state.
 4. Thedevice of claim 1 wherein said stimulator supplies sub thresholdstimulation periodically to said first lead system to alter tone wherethe level of sub threshold stimulation is selected to not arouse thepatient.
 5. The device of claim 1 wherein said stimulator supplies subthreshold stimulation periodically to said first lead system to elevateupper airway muscle tone where level of sub threshold stimulation isselected such that the patient is not aware of stimulation while patientis awake.